The present invention pertains to abrasive polishing compositions and associated methods of using these compositions for chemical mechanical planarization (CMP, also known as chemical mechanical polishing), wherein the slurry comprises stabilizer-surface-modified abrasive particles, for example colloidal silica surface modified with aluminum salt stabilizer, said stabilizer further having ligands bound thereto. The present invention also pertains to abrasive polishing compositions and associated methods of using these compositions for CMP wherein the slurry comprises stabilizer-organometallic compound-surface-modified abrasive particles, for example colloidal silica surface modified with aluminum salt stabilizer, said stabilizer further having ligands bound thereto, said ligands having a capacity to chelate one or more metal ions (e.g., ions comprising copper, cerium, iron, and selected other metals).
CMP for planarization of semiconductor substrates is now widely known to those skilled in the art and has been described in numerous patents and open literature publications. Some introductory references on CMP are as follows: “Polishing Surfaces for Integrated Circuits”, by B. L. Mueller and J. S. Steckenrider, Chemtech, February, 1998, pp. 38-46; “Integration of Chemical-Mechanical Polishing Into CMOS Integrated Circuit Manufacturing,” H. Landis et al., Thin Solids Films, 220 (1992), pages 1-7; and “Chemical-Mechanical Polish” by G. B. Shinn et al., Chapter 15, pages 415-460, in Handbook of Semiconductor Manufacturing Technology, editors: Y. Nishi and R. Doering, Marcel Dekker, New York City (2000).
In a typical CMP process, a substrate (e.g., a wafer) is placed in contact with a moving polishing pad, for example a rotating polishing pad attached to a platen. A CMP slurry, typically an abrasive and chemically reactive mixture, is supplied to the pad during CMP processing of the substrate. The abrasive may alternatively be partially or fully bound to the polishing pad. During the CMP process, the pad (typically fixed to the platen) and substrate are moved, typically by rotating both, while a wafer carrier system or polishing head applies pressure (downward force) against the substrate. The slurry or polishing liquid in combination with an abrasive polishing pad accomplishes the planarization (polishing) process by chemically and mechanically interacting with the substrate film being planarized due to the effect of the movement of the pad relative to the substrate. Polishing is continued in this manner until the desired film on the substrate is removed with the usual objective being to effectively planarize the substrate. Typically metal CMP slurries contain an abrasive material, such as silica or alumina, suspended in an oxidizing, aqueous medium.
Silicon based semiconductor devices, such as integrated circuits (ICs), typically include a dielectric layer. Multilevel circuit traces, typically formed from aluminum or an aluminum alloy or copper, are patterned onto the dielectric layer substrate. CMP processing is often employed in semiconductor manufacturing to remove excess metal at different stages. Various metals and metal alloys have been used at different stages of semiconductor manufacturing, including tungsten, aluminum, copper, tantalum, tantalum nitride, titanium, titanium nitride, ruthenium, platinum, iridium, and combinations thereof. For example, one way to fabricate a multilevel copper interconnect or planar copper circuit traces on a dielectric substrate is referred to as the damascene process. The utility of chelators in CMP has been recognized for decades. Water-soluble ligand containing organic compounds (also known as complexing agents or chelating agents) are used extensively in CMP formulations. During chemical mechanical planarization, these compounds can offer several advantages such as: a) increase metal removal rates by solubilizing abraded metal ions, b) stabilize the metal-ion-induced decomposition of hydrogen peroxide, c) can act as corrosion inhibitor to protect metal lines from galvanic corrosion, and d) reduce metal ion contamination defectivity by removing metal ions during CMP as well as during post-CMP steps.
It is known to use surface-modified abrasive in CMP. Colloidal silica, for example, has been modified with various metallic compounds as disclosed in U.S. Pat. Nos. 3,252,917, 3,620,978 and 3,745,126; commonly assigned published U.S. Patent Applications Nos. 2003/0162398, 2004/0006924, 2004/0029495, and 2005/0155296; EP Patent Publication 1 000 995; and also in the book entitled “The Chemistry of Silica”, R. K. Iler, Wiley Interscience (1979), pages 410-411. Abrasives such as silica, ceria and titania have been surface-modified with boron-containing compounds such as boric acid, as disclosed in commonly assigned U.S. Pat. No. 6,743,267 (having a common inventor with this application); commonly assigned U.S. Pat. No. 6,893,476 (having a common inventor with this application); U.S. Pat. No. 5,876,490; U.S. Pat. No. 5,472,493; and U.S. Pat. No. 6,776,810. It is known to attach metal ions which promote a Fenton-type reaction directly to abrasives, as is disclosed in commonly assigned U.S. Pat. No. 7,029,508. It is known to attach metal ions which promote a Fenton-type reaction to abrasives via the use of a stabilizer containing aluminum, boron, or tungsten disposed between the abrasive and the metal ions which promote a Fenton-type reaction, as is disclosed in commonly assigned U.S. Pat. No. 7,077,880. It is also known to use ligands bound to particles in CMP, as is disclosed in commonly assigned published U.S. application 2005/0076581, where the ligands are directly bound to the abrasive or are bound by a “spacer” such as a short hydrocarbon chain. Commonly assigned application Stabilizer-Fenton's Reaction Metal-Vinyl Pyridine Polymer—Surface Modified Chemical Mechanical Planarization Composition and Associated Method describes attaching a polyvinylpyridine to a particle. Other patents of interest include U.S. Pat. No. 3,620,978; U.S. Pat. No. 5,993,686; U.S. Pat. No. 6,471,735; and commonly assigned published U.S. Patent Applications No. 2004/0144038. The disclosures of each of these references are incorporated herein by reference thereto for all permissible purposes.
In order to achieve fast tungsten or copper removal rates, the use of oxidants and co-oxidants have been reported in the CMP patent literature. For tungsten CMP, oxidants such as periodic acid, potassium iodate, ferric nitrate, and hydrogen peroxide are commonly used. For copper CMP, hydrogen peroxide and hydroxylamine are commonly used oxidants. Of all the oxidants in commercial use, hydrogen peroxide is low cost, and it is benign from the standpoint of product stewardship, as the byproduct is water. However hydrogen peroxide is a poor oxidant for tungsten as it reacts very slowly, so an additive that can increase the polishing rate of tungsten with hydrogen peroxide during CMP is typically added. There have been a number of disclosures relating to soluble metal catalysts. See, for example, U.S. Pat. No. 5,958,288, which describes the use of soluble metal co-catalysts for activating hydrogen peroxide for the planarization of tungsten. See also Patent No. SU 1629353, which discloses a composition and method for CMP of aluminum alloys, wherein soluble iron (iron chloride) is used to activate sodium perborate in the presence of diethyldithiophosphoric acid and ninhydrin. Patent Publication No. WO 99/53532 recited as one embodiment of the invention a CMP slurry comprising water, abrasive particles, and an oxidizing solution comprising a soluble peroxide, an amino acid, and one or more metals and/or compounds containing metals selected from the group consisting of chromium, cobalt, copper, iron, lead, nickel, palladium, rhodium, samarium, and scandium, with copper being preferred. This application recites that “the use of metals and/or compounds containing metals in combination with water soluble peroxide and amino acid results in the accelerated generation of hydroxyl radicals and yields a much more effective polishing composition.
While the use of soluble metal ions increases the speed at which hydrogen peroxide reacts with copper or tungsten, they also require CMP slurries with large concentrations of dissolved (ionic) metallic components. As a result, the polished substrates can become contaminated by the adsorption of charged metal ions. These species can migrate and change the electrical properties of the devices, for example at gates and contacts, and change the effective dielectric properties of dielectric layers. These changes may reduce the reliability of the integrated circuits with time. Therefore, it is desirable to expose the wafer only to high purity chemicals with very low concentrations of mobile metallic ions. Chelators used in such a polishing slurry can reduce contamination, but the chelators chelate the metal ions and generally reduce the efficacy of the soluble metal ions.
Even though there are several advantages of using complexing and chelating agents in CMP formulations in solution phase, there are several other disadvantages of using these compounds in soluble form such as: a) due to strong bonding, and high molecular mobility, these compounds can form complexes on the metal line surface, which are difficult to remove from the surface, b) chelating agents can electro-migrate to bulk metal circuit and such agents are extremely difficult to remove during cleaning step, and c) chelating agents can increase etch rate, hence metal line dishing, and trenching. Another disadvantage is that the presence of chelators makes the separation and recovery of metal ions, for example the metal ions polished from the surface of the substrate, from the used slurry very difficult and costly. As a result, metals are often not recovered from this waste stream, and the waste stream must often be treated under stringent environmental guidelines which add significantly to disposal costs. The present invention is adapted to reduce or remove these disadvantages.